<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    let str='JS5353654656你知道555啦啦啦'

    // 正向断言
    const reg=/\d+(?=啦)/
    const reg2=/(?=么)\d+/

    const res=reg.exec(str)
    const res2=reg2.exec(str)

    console.log(res)
    console.log(res2)
</script>
</body>
</html>
